Performance of Wood Steel Hybrid Multistorey Buildings

Uploaded by

Description:

This paper involves detailed study on performance of timber based wood steel hybrid multistorey buildings. This paper examines the performance of wood steel hybrid multistorey buildings for regions with high seismic hazard indexes based on certain criteria like time period, base shear and displacement of the system. Different wood-steel hybrid models are modelled and analysed using finite element based software SAP2000 to predict structural response, more effective and economic way of implementing shear walls in the design. The wood steel hybrid structure incorporates Cross Laminated Timber (CLT), Oriented Strand Boards and Steel as shear walls in steel moment frames. Static analysis and Dynamic analysis are performed on the structure and it is observed that shear walls significantly reduce the time period, base shear and displacement of the steel frame. Parametric studies have been carried out on hybrid wood steel structures with different materials for varying panel configuration (Alternate bays, Middle bays and Every bays). The use of hybrid wood and steel systems allows for the combination of high strength and ductility of the steel frame with high rigidity and light weight of the hybrid structures. The focus of the analysis is on comparing the key structural performances between different cases including displacement, time period and base shear. The different loads considered were dead load, live load, seismic loads, and their load combinations as per IS:1893 (Part-I) 2002.
Keyword: Lightweight structure, cross laminated timber, oriented strand boards, dynamic performance, time period, base shear, displacement.

Available Formats

Performance of Wood Steel Hybrid Multistorey Buildings

Uploaded by

Description:

This paper involves detailed study on performance of timber based wood steel hybrid multistorey buildings. This paper examines the performance of wood steel hybrid multistorey buildings for regions with high seismic hazard indexes based on certain criteria like time period, base shear and displacement of the system. Different wood-steel hybrid models are modelled and analysed using finite element based software SAP2000 to predict structural response, more effective and economic way of implementing shear walls in the design. The wood steel hybrid structure incorporates Cross Laminated Timber (CLT), Oriented Strand Boards and Steel as shear walls in steel moment frames. Static analysis and Dynamic analysis are performed on the structure and it is observed that shear walls significantly reduce the time period, base shear and displacement of the steel frame. Parametric studies have been carried out on hybrid wood steel structures with different materials for varying panel configuration (Alternate bays, Middle bays and Every bays). The use of hybrid wood and steel systems allows for the combination of high strength and ductility of the steel frame with high rigidity and light weight of the hybrid structures. The focus of the analysis is on comparing the key structural performances between different cases including displacement, time period and base shear. The different loads considered were dead load, live load, seismic loads, and their load combinations as per IS:1893 (Part-I) 2002.
Keyword: Lightweight structure, cross laminated timber, oriented strand boards, dynamic performance, time period, base shear, displacement.

Abstract: This paper involves detailed study on performance of timber based wood steel hybrid multistorey buildings. This paperexamines the performance of wood steel hybrid multistorey buildings for regions with high seismic hazard indexes based oncertain criteria like time period, base shear and displacement of the system. Different wood-steel hybrid models are modelled andanalysed using finite element based software SAP2000 to predict structural response, more effective and economic way ofimplementing shear walls in the design. The wood steel hybrid structure incorporates Cross Laminated Timber (CLT), OrientedStrand Boards and Steel as shear walls in steel moment frames. Static analysis and Dynamic analysis are performed on thestructure and it is observed that shear walls significantly reduce the time period, base shear and displacement of the steel frame.Parametric studies have been carried out on hybrid wood steel structures with different materials for varying panelconfiguration (Alternate bays, Middle bays and Every bays). The use of hybrid wood and steel systems allows for thecombination of high strength and ductility of the steel frame with high rigidity and light weight of the hybrid structures. Thefocus of the analysis is on comparing the key structural performances between different cases including displacement, timeperiod and base shear. The different loads considered were dead load, live load, seismic loads, and their load combinations asper IS:1893 (Part-I) 2002.Keyword: Lightweight structure, cross laminated timber, oriented strand boards, dynamic performance, time period, base shear,displacement.

I. INTRODUCTIONA hybrid system is a combination of two or more structural materials. Steel and concrete hybridization is the most common type ofhybrid system. Steel structures are very common in the world because of its short duration of construction and high strength. Toimprove resistance and to overcome other limitations of individual steel structure it can be combined with other materials likehybrid systems. This project involves detailed study of hybrid wood-steel structures and its application in the construction industry.Wood and steel effective hybridization creates a system in which only minimum steel is used where high strength and ductility arerequired. Steel is much stronger and provides significant post-yield deflection capability, known as ductility. Steel frames areextremely ductile, with large deformations during seismic events. Wood shear walls are also provided for buckling resistance of thebuilding. Wood shear wall contributes to the stiffness and strength of the steel frames thus increasing stiffness and strength ofHybrid Wood-Steel Structure. Benefits include increase in tensile capacity, seismic performance of the structure, and cost savings.Hybrid systems design is often considered for aesthetic purpose, sustainability, optimal use of different material properties. Thehybrid materials can be integrated at component levels (hybrid slab/diaphragms, hybrid beams, hybrid columns, hybrid diagonals,hybrid post-tensioned joints) and/or at the building system levels (hybrid frames, hybrid system of steel frames and wooddiaphragms, vertical mixed system and hybrid trusses). To elaborate on these types of hybridization and their advantages andchallenges, case studies of steel-timber are provided. The considered software package is SAP2000. Modelling of Hybrid Wood-Steel Structures and analysis is done by using SAP2000 software. In SAP2000 Static Analysis and Dynamic Analysis is performedand the effect of shear wall on the structure is also studied.

II. METHODOLOGYFig. 1 shows plan of Hybrid Wood-Steel building 24m x 36m. Case studies using (G+3) and (G+7) hybrid buildings will benumerically modelled (Fig.2). For the formation of hybrid structure Steel, Cross Laminated Timber and Oriented Strand Board areused. First storey height of each building was 4 m and all other storeys were 3m height. Components include beams, columns, slaband shear walls. Beams are the flexural member in the buildings. It can transfer the loads to columns. The material used for theconstruction of beams is steel which is an I-section. Beams are having cross section W310 x 254 x 86 kg/m (Nominal Depth x

Width x Weight). Columns are the compression members, which has the capacity to transfer the loads from beams. The materialused for the construction of columns is steel which is an I-section. Columns are having cross section W310 x 313 x 179 kg/m(Nominal Depth x Width x Weight). Slab is a flat piece of wood serves as a walking surface. The thickness of the slab considered is150mm.

Fig. 1. Plan of Hybrid Wood Steel Buildings

Shear walls are vertical elements of the horizontal force resisting system. A shear wall is a wall which is designed to resist shear,lateral force which causes the bulk of damage in earthquakes. The thickness of the shear wall is 100mm. Loads combinationsconsidered including dead load, live load and seismic loads. Details of the loads and load combination are taken as per IS: 1893(Part-I) 2002. (G+3) and (G+7) hybrid building 3-D finite element models with SAP2000 were used to predict structural responsesunder these loads. Numerical model using floor and wall components were modelled as four node shell elements. Beam and Columncomponents were modelled as line elements. Dynamic analysis via response spectrum method is used to apply seismic loads on thestructure. The frequency and acceleration are taken corresponding to seismic zone V.

III. MATERIALS AND PROPERTIES USED FOR THE FORMATION OF HYBRID BUILDINGSA. Steel (ASTM A36)Steel is the main material used for the formation of the building. Steel is a material which has good ductility and good strength.Properties of steel referred from American standards for Material Testing [13]. TABLE I PROPERTIES OF STEEL (ASTM A36)

Properties Steel Units

B. Cross Laminated Timber (CLT)

Cross Laminated Timber is a multi-layer mass timber product made from gluing layers of solid-sawn lumber together. Each layersof boards are oriented perpendicular to adjacent layers, so that the panels are able to achieve better structural rigidity in bothdirections. Properties of Cross Laminated Timber referred from Canadian Technical Design Guide [14] and ascelibrary.org [15]. TABLE II PROPERTIES OF CLT Properties CLT Units

Density 485 Kg/m3

C. Oriented Strand Board (OSB)

OSB is a mat-formed panel product made of strands bonded with exterior type resins under heat and pressure. OSB panels consist offour or five layered mats. Properties of OSB are referred from the link [16] and [17]. TABLE III PROPERTIES OF OSB Properties OSB Units

IV. RESULTS & DISCUSSION

Analysis of G+3 and G+7 Hybrid wood-steel multistorey building with different shear wall material in various positions and theresults are compared. The models of the building is analyzed for static structural analysis and dynamic analysis.(Fig. 3 & 4) shows the time Period for both G+3 and G+7 buildings installed with OSB, CLT and STEEL shear walls. It is observedthat time period of steel frame without shear walls is more and with shear walls is less. It can be seen that for (G+3) hybrid buildingcases, CLT wall system has much lower time period relative to STEEL wall system. For G+3 building in alternate bays, time periodfor STEEL shear walls is 0.19 seconds and 0.123 seconds (35 % less) for the CLT shear walls. Also time period for OSB shear wallsis 0.23 seconds and 0.19 seconds (17 % less) for STEEL shear walls. Difference between time period values of OSB, CLT andSTEEL shear walls installed in alternate bays and every bays is also minimum whereas time period of all the shear wall materialsinstalled in middle bays is more as compared to alternate bays and every bays.It is observed that for (G+7) buildings time period of steel frame significantly reduced after using shear walls in all three cases.Time period of models installed with CLT and STEEL shear walls in Alternate Bays is less as compared to oriented strand boardshear walls. For G+7 building in Alternate Bays, time period for CLT shear walls is 0.262 seconds and 0.19 seconds (27 % less) forthe STEEL shear walls, whereas time period in Every Bays for STEEL shear walls is 0.188 seconds and 0.186 seconds (l% less) forthe CLT shear walls which is a minimum difference.

Table VI & VII shows that displacement of the steel frame significantly reduced after using shear walls. For (G+3) HybridBuildings displacement is reduced by 73.58% in X-direction and 81.3 % in Y-direction of steel frame when cross laminated timbershear walls installed in alternate bays. Whereas Displacement is reduced by 73.24% in X-direction and 81.41 % in Y-direction ofsteel frame when cross laminated timber shear walls installed in every bays. For (G+7) Hybrid Buildings displacement is reduced by81.75 % in X-direction and 83.88 % in Y-direction of steel frame when cross laminated timber shear walls installed in alternatebays. Whereas Displacement is reduced by 86.9% in X-direction and 88 % in Y-direction of steel frame when cross laminatedtimber shear walls installed in every bays. The percentage difference between displacement values in alternate bays and in every

bays is minimum. Displacement in X and Y directions of models installed with cross-laminated timber and steel shear walls inAlternate Bays, Middle Bays and in Every Bays is less as compared to oriented strand board walls.

V. CONCLUSIONSAnalysis results showed that the time period, displacement of the steel frame significantly reduced after using shear walls. Timeperiod of (G+3) hybrid building installed with cross-laminated timber and steel shear walls is less as compared to OSB, howeverthere is a minimum difference between time period values of OSB, CLT and STEEL shear walls when used in alternate bays and inevery bays respectively as observed from (Fig 3). Time period of (G+7) hybrid building installed with cross-laminated timber andsteel shear walls is less as compared to OSB. Difference between time period values of (G+7) hybrid building installed with Steeland CLT shear walls is also minimum when used in alternate bays and every bays (Fig 4). Therefore oriented strand board andcross-laminated timber can be used in place of steel in alternate bays as it is cheap. Through the proper use of oriented strand boardand cross-laminated timber shear walls, we can obtain a light weight hybrid structure and stiffness much greater than that of typicalsteel shear walls. Stiff and light weight hybrid building performs much better than the steel building under earthquake loads sinceforces in an earthquake are proportional to the weight of the structure. The result of the study indicates that cross-laminated timberand oriented strand board walls greatly reduces base shear relative to the steel shear walls. After analyzing all the result parameters,it was observed that wood and steel hybrid structure having wooden shear walls installed in the alternate bays model showed thebest performance in all cases. Considering from cost and aesthetic view models with wood shear wall in alternate bays consumesless material and hence it is economical. Overall the system shows significant promise for future construction.

VI. ACKNOWLEDGMENTI wish to acknowledge my deep sense of gratitude to my guide Professor Roshni John, Head of Civil Engineering Department,Saraswati College of Engineering, Kharghar – 410210, India. Her constant encouragement enabled me to work enthusiasticallythroughout the project work. She has always been a source of knowledge and inspiration to me and I owe a lot for her kindness,invaluable guidance and precious time, which she spent in guiding me. I would also like to acknowledge the help, unconditionalsupport and motivation received from my colleagues during my work. Finally, I wish to express my deepest gratitude to my familywho gives me more loving devotions than I could ever return in a lifetime.